In the clock example, I would like to simply press-hold a key and a custom desktop clock appears (program start) and then disappears (program quit) when I release the key. Defining many tasks in this manner would prevent the need for having multiple tasks running and eating cpu/ram when occasionally 'checking in' super-quickly on something is all that's required.

Perhaps I should've clarified that this was an example that can be modified to suit your needs & I only tested it on my XP box, sorry about that.Anyway, I've made an adjustment to the window & it should work as desired. (e.g. "Date and Time Properties" on XP & "Date and Time" on > Vista)